The present invention relates to a semiconductor device as defined in the preamble of Claim 1.

As is known, an electronic semiconductor device, for example, an integrated circuit, is formed by a chip of semiconductor material which contains the active portions of the device, and by a structure for supporting the chip and for forming electrical interconnections enabling the device to be connected to an external circuit.

Upon completion of its manufacture, the chip has a surface covered by a layer of insulating material on the surface of which metal interconnection elements appear in the form of pads which constitute the terminals of the electronic device.

An interconnection technique known as the "flip-chip" technique provides for a flat mounting substrate of insulating material on which there are metal tracks which terminate in areas arranged in a configuration mirroring that of the pads on the chip. A soldering material, for example an alloy of lead and tin, is applied to the pads and, typically, takes the form of a hemispherical projection (a bump) on each pad. The chip is then placed on the mounting substrate with the pads surmounted by the bumps in register with the terminal areas of the metal tracks. The assembly is brought to the melting point of the soldering material so that the soldering material melts and, after cooling, solders the pads of the chip to the corresponding metal areas of the substrate. Finally, a thermosetting resin capsule is formed, incorporating the chip.

In comparison with another widely used interconnection technique which uses thin wires soldered at one end to the pads of the chip and at the other end to the metal terminals which form part of a terminal structure (a lead frame) which surrounds the chip, the "flip-chip" technique has various advantages. In particular, it enables contact pads to be arranged over the entire area of the chip and not only along the perimeter as is necessary with the other technique, it permits very short interconnections and, finally, it takes up little space. However, it is not suitable for use in power applications in which the chip of semiconductor material is subject to a very high degree of heating since very little heat is dissipated from the chip to the substrate. The chip is in fact joined to the substrate only by a few points with low thermal resistance which are the soldering points, whereas most of its surface is separated from the substrate by a space which is filled with the resin in which the chip is incorporated. Although the space is very shallow, the heat dissipation is limited by the relatively high thermal resistance of the resin.

In order to reduce the thermal resistance of the resin, it is known to include therein particles of material having lower thermal resistance, but even this measure does not greatly improve the performance of the device in power applications.

Patent Abstract of Japan JP 62144346 describes a flip chip technique which reflects the content of the precharacterising portion of claim 1.

The object of the present invention is to propose a semiconductor device which can be connected by the "flip-chip" technique and which has good performance in power applications.

This object is achieved by the provision of the semiconductor device defined and characterized in Claim 1. Particular embodiments of the invention are defined by the dependent claims.

The invention will be understood better from the following detailed description of an embodiment thereof, given by way of non-limiting example with reference to the appended drawings, in which:

• Figure 1 shows, in perspective, a device according to the prior art being mounted on a mounting substrate by the "flip-chip" technique,
• Figure 2 shows, in section, a semiconductor device according to the prior art soldered onto a mounting substrate and encapsulated,
• Figure 3 shows, in perspective, a semiconductor device according to the invention being mounted on a mounting substrate, and
• Figure 4 shows, in section, a semiconductor device according to the invention, soldered to a mounting substrate.

Upon completion of the manufacturing process, a known semiconductor device appears as shown in Figure 1, in which it is generally indicated 10.

It is formed by a chip 11 of semiconductor material, for example, silicon, with a surface covered by a layer 12 of insulating material, for example, silicon dioxide. Substantially coplanar metal pads 13 which are the ends of the electrical connections to the active portions of the electronic device, appear on the surface 12 and are surmounted by bumps 14 of soldering material, for example, an alloy of lead and tin.

The device 10 is ready to be mounted on a flat mounting substrate 20 of insulating, for example, ceramic material on which there are metal tracks 21 which terminate, on the upper surface of the substrate 20, in areas 22 arranged in the same configuration as the pads 13 of the device 10. The metal tracks 21 in this example extend over the edges of the substrate 20 in order to be soldered to a printed circuit board, not shown. In another application, the substrate could itself be a printed circuit board. In yet another application, the mounting substrate could have interconnection elements which extend through its entire thickness and terminate in contact areas on both of its faces.

Figure 2 shows the device 10 on the mounting substrate 20 after the pads 13 have been soldered to the terminal areas 22 of the metal tracks 21 by means of the soldering material of the bumps 14. As can be seen, the pads 13 are the end surfaces of metal interconnection elements which extend through the insulating layer 12 from contact areas of the chip 11 of semiconductor material to the surface of the layer 12. Moreover, some of the interconnection elements may not be in contact with areas of the chip but with contact areas of electrically-conductive elements electrically insulated from the chip, for example, gate electrodes or capacitor electrodes.

The next manufacturing step consists of the application of a drop 25 of thermosetting resin, for example, an epoxy resin, which may be filled with grains of silica to increase its thermal conductivity, and which flows into the space 26 between the opposed surfaces of the device 10 and of the substrate 20 and encloses the entire chip, sealing it on the substrate and insulating it from the outside environment.

In Figures 3 and 4, in which elements identical or corresponding to those of Figures 1 and 2 are indicated by the same reference numerals, the semiconductor device according to the invention has a metal plate 30 extending over the layer of insulating material 12. In this embodiment, the plate 30 is partially incorporated in the layer of insulating material 12 so as to have an extensive uncovered surface substantially coplanar with the pads 13. The plate 30 is arranged in the region of a power component of the electronic device formed in the chip 11 and may be formed by the same steps of the manufacturing process by which the metal connections which terminate on the surface in the pads 13 are formed. Moreover, it may be completely insulated from the surface of the chip 11 of semiconductor material, or it may be in contact with a predetermined area thereof. In this latter case, the plate 30 constitutes a terminal of the device.

Bumps 31 similar to those, indicated 14, formed on the pads 13, are formed on the plate 30. The bumps 14 and 31 can be formed simultaneously and by the same manufacturing steps, for example, by a galvanic deposition (electroplating) process. Alternatively, if a screen printing process is used, it is advantageous to form a single element of soldering material on the plate 30, that is, a layer of soldering material over its entire surface.

The mounting substrate 20 of Figure 3 differs from that of Figure 1 in that it contains a metal element 35 which has a relatively extensive surface, to which the plate 30 of the device 10 is soldered, as shown in Figure 4.

The metal element 35 extends through the entire thickness of the mounting substrate 20 and can be put into contact with an external heat sink, not shown, by means of its opposite surface to that which is soldered to the device 10. With this structure, it is possible to achieve very efficient dissipation of the heat generated by the semiconductor device in operation.

Naturally, the metal element 35 may have a different structure, for example, it could extend only on the surface of the substrate 20 without extending through it. In any case, the efficiency of the heat dissipation is much greater than that which can be achieved by the known technique, by virtue of the low thermal resistance of the metal contacts and the relatively large extent of the contacting metal surfaces.